LTC3636 datasheet(21/28 Pages) LINER

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LTC3636/LTC3636-1

3636fb

For more information www.linear.com/LTC3636

A standard value of 0.33µH should work well here. Solv-

ing the same equation for channel 2 results in a 0.47µH

inductor.

COUT will be selected based on the charge storage require-

ment. For a VDROOP of 90mV for a 6A load step:

COUT1 ≈

3 • ΔIOUT

f • VDROOP

3 • (6A)

(2MHz)(90mV)

= 100µF

Two 47µF ceramic capacitor should be used for channel 1.

Solving the same equation for channel 2 (using 5% of

VOUT for VDROOP) results in 55µF of capacitance (47µF is

the closest standard value).

CIN should be sized for a maximum current rating of:

IRMS = 6A

1.8V 13.2V − 1.8V

(

)

13.2V

= 2.1A

APPLICATIONS INFORMATION

Solving this equation for channel 2 results in an RMS

input current of 2.8A. Decoupling each VIN input with

a 47µF ceramic capacitor should be adequate for most

applications.

Lastly, the feedback resistors must be chosen. Picking

R1 and R3 to be 13.7k, R2 and R4 are calculated to be:

R2 = (13.7k) •

1.8V

0.6V

– 1

⎛

⎝

⎜

⎞

⎠

⎟ = 27.4k

R4 = (13.7k) •

3.3V

0.6V

– 1

⎛

⎝

⎜

⎞

⎠

⎟ = 61.9k

The final circuit is shown in Figure 8.

RUN1

RUN2

TRACKSS2

PGOOD2

LTC3636/

LTC3636-1

GND

TMON

BOOST2

3636 F08

0.1µF

0.68µH

SW2

VIN2 VIN1

VFB2

TRACKSS1

PGOOD1

BOOST1

SW1

VFB1

COUT2

47µF

VOUT2

3.3V AT 6A

0.1µF

0.33µH

13.7k

COUT1

47µF

×2

VOUT1

1.8V AT 6A

VIN

12V

CIN

47µF

×2

162k

27.4k

13.7k

61.9k

RCOMP1

11k

CBYP1

10pF

CCOMP1

330pF

CF1

33pF

CF2

22pF

MODE/SYNC

ITH1

RCOMP2

10.5k

CBYP2

10pF

CCOMP2

220pF

ITH2

INTVCC

4.7µF

Figure 8. Design Example Circuit

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